Color negative films are a class of photosensitive materials that map the luminance (neutral) and chrominance (color) information of a scene to complementary tonal and hue polarities in the negative film. Light areas of the scene are recorded as dark areas on the color negative film, and dark areas of the scene are recorded as light areas on the color negative film. Colored areas of the scene are recorded as complementary colors in the color negative film: red is recorded as cyan, green is recorded as magenta, blue is recorded as yellow, etc. In order to render an accurate reproduction of a scene, a subsequent process is necessary to reverse the luminance and chrominance information back to those of the original scene. This subsequent process may or may not require another photosensitive material.
In the motion picture industry, there are two common subsequent processes. One such subsequent process is to optically print the color negative film onto another photosensitive material, such as Eastman Color Print Film 5386.TM., to produce a color positive image suitable for projection. Another subsequent process in the motion picture industry is to transfer the color negative film information or the color print film information into a video signal using a telecine transfer device. Various types of telecine transfer devices are described in Engineering Handbook, E. O. Fritts, Ed., 8th edition, National Association of Broadcasters, 1992, Chapter 5.8, pp. 933-946, the disclosure of which is incorporated by reference. The most popular of such devices generally employ either a flying spot scanner using photomultiplier tube detectors, or arrays of charged-coupled devices, also called CCD sensors. Telecine devices scan each negative or positive film frame transforming the transmittance at each pixel of an image into voltage. The signal processing then inverts the electrical signal in the case of a transfer made from a negative film in order to render a positive image. The signal is carefully amplified and modulated, and fed into a cathode ray tube monitor to display the image, or recorded onto magnetic tape for storage.
In the motion picture industry, the same color negative films are conventionally used for both subsequent processes, optical printing and telecine transfer to a video signal. In order to obtain a high quality visual image in an optical print, it is normally desirable that the contrasts, or slopes of the characteristic curves (that is, the density vs. log Exposure, or D log E curves), for all color records are matched or substantially the same as illustrated by the dotted lines in FIG. 3, which depict the blue (top dotted line), green (middle dotted line), and red (bottom dotted line) characteristic curves for a color negative film with closely matched contrasts. This ensures that objects having neutral tone in the original scene are recorded with neutral tone on the negative film and on optical prints made thereof, regardless of the exposure level. Mis-matched contrasts in the color records of a negative film would result in the production of images in a positive print which do not faithfully reproduce the colors of the original scene. Pictures such as these would be deemed to be of low quality in the industry. For the purposes of this invention, unless otherwise defined herein, the term "contrast" shall refer to the Best Fit Contrast Parameter for color negative films, which is defined as the slope of a line connecting a point at minimum density plus 0.20 to a point at 1.35 log Exposure greater than the first point on a status M density vs. log Exposure curve for a color record.
It has been found, however, that negative films designed for optical printing onto on a positive print material such as Eastman Color Print Film 5386.TM. may require substantial individual color correction when used in making telecine transfer positives. This has been found to be a result of the peak spectral absorbance wavelength of the image dyes generated in the color records of conventional color negative films not substantially matching the peak spectral responses of typical telecine transfer devices. This is illustrated in FIGS. 1 and 2. FIG. 1 illustrates the spectral response of the blue, green and red channels of a typical telecine transfer device, while FIG. 2 illustrates the spectral characteristics of typical imaging dyes formed in a color negative film. The red channel of the telecine device monitors the color negative cyan dye far off of its peak density. This results in a signal with greatly reduced modulation of the changes in dye density. Also, the red channel records as red a certain proportion of the green record because the red channel detects the long wavelength side of the magenta imaging dye. Depending on the spectral response of the electronic image capture device used, other channel cross contaminations are possible. The resultant image is then comprised of a red signal which has sufficiently low modulation relative to the blue and green signals. Further, this red signal is contaminated with a low modulation green channel.
While color print films have been designed specifically for use in making positives for telecine transferring, use of such print films adds additional processing steps and costs to forming a telecine transfer, and image information from the color negative can be lost in the print step. Accordingly, it would be desirable to make improved telecine transfers possible directly from a color negative film.